The nanostructure of relaxor ferroelectric materials has been a central focus for investigating the microscopic origin of their intriguing physical properties. While it is believed that relaxor ferroelectricity is governed by polar nanostructures, such as polar nanoregions or nanodomains, recent studies have indicated the importance of additional mechanisms, such as the competition of ferroelectric/anti-ferroelectric order and the formation of hierarchical nanodomains. This calls for further investigation on the nanostructure. Here, we used conventional, in situ, and atomic-scale electron microscopy to study prototypic relaxor ferroelectrics, Pb(Mg1/3Nb2/3)O-3(PMN) and Pb(Mg1/3Nb2/3)O-3-PbTiO3(PMN-PT). We found that a lamellar-like nanostructure was present in pure PMN, which had been overlooked in past studies and did not have a strong correlation with the polar nanostructure and the chemically ordered region. Unlike the lamellar-like nanodomains in PMN-PT, the lamellar-like nanostructure in PMN was not coupled with Pb-ion displacement and was not reoriented by the presence of an electric field. The results suggested that the formation of a lamellar-like structure occurs prior to the formation of larger-scale polar order in relaxor ferroelectrics.